I'm running a Tornado webserver and using ZooKeeper to store some metadata and 
occasionally the ZooKeeper connection will error out irrevocably.  Any 
subsequent calls to ZooKeeper from this process will result in a SystemError.

Here is the relevant portion of the Python traceback:
  File "/usr/lib/pymodules/python2.5/zuul/storage/zoo.py", line 69, in call
    return getattr(zookeeper, name)(self.handle, *args)
SystemError: NULL result without error in PyObject_Call

I found this in the ZooKeeper server logs:

2010-07-13 06:52:46,488 - INFO  
[NIOServerCxn.Factory:$fact...@251] - 
Accepted socket connection from /
2010-07-13 06:52:46,489 - INFO  
[NIOServerCxn.Factory:] - Client 
attempting to renew session 0x429b865a6270003 at /
2010-07-13 06:52:46,489 - INFO  
[NIOServerCxn.Factory:] - Revalidating client: 
2010-07-13 06:52:46,793 - INFO  
[QuorumPeer:/0:0:0:0:0:0:0:0:2181:nioserverc...@1424] - Invalid session 
0x429b865a6270003 for client /, probably expired
2010-07-13 06:52:46,794 - INFO  
[NIOServerCxn.Factory:] - Closed socket 
connection for client / which had sessionid 0x429b865a6270003

The ZooKeeper ensemble is healthy; each node responds as expected to the four 
letter word commands and a simple restart of the Tornado processes "fixes" this.

My question is, if this really is due to session expiration why is a 
SessionExpiredException not raised?  Another question, is there an easy way to 
determine the version of the ZooKeeper Python bindings I'm using?  I built the 
3.3.0 bindings but I just want to be able to verify that.

Thanks for the help,


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